Tensioning device



Oct. 13, 1970 BN1. COOPER ETAL 3,533,574

TENSIONING DEVICE Filed March 25, 1968 3 Sheets-Sheet 1 III FIG.2

Oct. 13, 1970 B, J, COOPER ETAL 3,533,574

TENS IONING DEVI GE 3 Sheets-Sheet 2 Filed March 25, 1968 FIG.3

Oct. 13, 1970 COOPER ETAL 3,533,574

TENSIONING DEVICE Filed March 25, 1968 3 Sheets-Sheet 5 /l/ l I -FIG.4

nited States atent Qfice 3,533,574 Patented Oct. 13, 1970 US. Cl.242-450 3 Claims ABSTRACT OF THE DISCLOSURE A tensioning device foryarns, threads, wires cables, etc., is operated by fluid pressure andcontrolled by a feedback arrangement responsive to changes in backpressure in an open nozzle induced by the thread tension.

This invention relates to tensioning devices.

The term tensioning device is to be understood to mean a device forimparting tension to a thread and for maintaining a predeterminedtension in the thread. The term thread is used herein for convenience,but it is to be taken to include any flexible elongate member consistingof one or more threads of textile and fibrous material, whether naturalor synthetic; metallic threads or wires, and so on; and includes twistedthreads, metallic and partly-metallic cables, insulated wires andcables, spun and unspun fibres and yarns, and the like.

According to the invention, a tensioning device includes fluid-pressureoperated variable tensioning means ar ranged to impart tension to athread, and feedback means responsive to changes in the output tensionin the thread for varying the fluid pressure so as to adjust thetensioning means in a manner tending to cancel said changes.

According to a preferred feature of the invention, said feedback meansinclude a nozzle arranged to be supplied with pressurized fluid,resilient means arranged for resilient movement resiliently in responseto changes in the output tension, the resilient means being in front ofthe nozzle so that said movement changes the back pressure at thenozzle, and the nozzle being connected to the tensioning means so thatchanges in said back pressure can be transmitted to the tensioning meanswhereby to adjust the tensioning means in said manner.

There may be provided between the nozzle and the tensioning means afluidic amplifier arranged to control the input pressure to thetensioning means in response to said back pressure.

Said resilient means may for example be a leaf spring or diaphragm.

Tensioning devices according to the invention are applicable, in variousappropriate forms, to such apparatus as (for example) spinningmachinery, machinery for making synthetic textile fibres, coil-windingmachinery, wire-winding machinery, rope-making apparatus (whether forwire or fibre ropes), cable-making machinery for electrical and othercables including heavy wire cables and hawsers, submarine cable layingapparatus, and apparatus for winding prestressing wires into positionduring the building of a prestressed concrete structure or fabricationof prestressed concrete components.

In adapting devices according to the invention for use with threads ofsuch widely-differing sizes and mechanical properties, the tensioningmeans, and the means by which the feedback means is made responsive tothe output tension, will be designed so as to suit the particular threadto be tensioned.

According to a preferred feature of the invention in one aspect, thetensioning means includes first threadengaging means moveable with aresilient fluid-pressure sensitive member towards and away from secondthreadengaging means arranged so that the thread is pinched between saidfirst and second thread-engaging means.

The pressure-sensitive member is preferably a bellows.

Tensioning means of this kind are more suitable for small threads suchas textiles (e.g. wool) and thin wires, having a fairly high degree offlexibility.

According to a preferred feature of the invention in another aspect, thetensioning means include a capstan drum, arranged for the thread to passtherearound, and a fluid-pressure operated brake coupled to the capstandrum.

Tensioning means of this kind are suitable for heavy threads such asprestressing cables, wire ropes and large electric cables, though theycan readily be adapted for smaller threads as well.

The larger the thread to be tensioned, the greater will be the tensionrequired, as a general rule. Thus tensioning devices according to theinvention, where they are designed for use with the larger types ofthread such as prestressing cables, etc., may require substantial fluidpressures to operate the tensioning means. The size of the components ofthe feedback equipment can be kept to a minimum by the use of a fluidicamplifier as mentioned above: where a very large amplification isrequired, for supplying relatively high pressures to the tensioningmeans, the amplifier may be in several stages. A cascade or series ofseparate fluidic amplifiers, giving progressively greater amplification,is to be taken as included within the scope of the term fluidicamplifier.

Various devices according to the invention will now be described by wayof example and with reference to the accompanying drawings, of which:

FIG. 1 is a diagrammatic view showing such a device in one form;

FIG. 2 is a diagrammatic view showing a modified form of the device;

FIG. 3 is a diagrammatic view showing another form of the device;

FIG. 4 is a sectional view taken on the line IV-IV of FIG. 5, showing analternative form of tensioner to that used in the devices shown in FIGS.1 and 2;

FIG. 5 is a sectional view taken on the line VV of FIG. 4; and

FIG. 6 is a sectional view showing a modification of the tensioner shownin FIGS. 4 and 5.

With reference to FIG. 10, a woolen thread 10, passes in the directionindicated by the adjacent arrow through a tensioner 11 including twosuccessive fixed bars 12 spaced apart in the direction of motion of thethread (which passes over them and is in contact with them). vA thirdbar 13 is situated between the bars 12 and engages the opposite side ofthe thread. The bar 13 is mounted in the tensioner 11 by means of abellows 14. Expansion of the bellows 14 kinks the thread so as toincrease its tension, and contraction of the bellows decreases thetension.

Expansion andcontraction of the bellows 14 is controlled by apressurised fluid supplied from a source (not shown) through an orifice15 and a pipe 16 communicating with the interior of the bellows.

Beyond the tensioner 11, the thread 10 passes through a loop 17supported from the free end of a cantilevered leaf spring 18. The spring18 serves as a tension-sensing device, in that it is deflected by anyincrease in the tension of the thread 10. A nozzle 19 is arrangedadjacent the spring 18, in a position in which it is closed, or mostnearly closed by the spring 18 when the output tension in the thread 10(i.e. the tension after passing through the bars 12 and 13) is zero. Thenozzle 19 is supplied with pressurised fluid through the same orifice 15as in the bellows 14.

In operation, the output tension in the thread is preset to apredetermined value by setting the fiuid pressure at a correspondingvalue. This may be done either at its source, or for example by varyingthe size of the orifice 15, which may be made adjustable for thispurpose.

If the output tension is increased for any reason (such as an increasein the diameter of the thread 10 as it passes through the tensioner 11),or an increase in input tension of the thread, the spring 18 isdeflected away from the nozzle 19 by a corresponding amount, so reducingthe back pressure in the nozzle. Since this back pressure is also thepressure in the bellows 14, the bellows contract, so restoring theoriginal output tension in the thread and enabling the spring 18 at thesame time to move back to where it was. Thus the spring 18 and nozzle 19together act as a negative feedback device, tending always to maintainthe fluid pressure in the bellows 14 at a value corresponding to therequired output tension in the thread.

The device shown in FIG. 2 is similar to that shown in FIG. 1, but itincorporates a fluidic proportional amplifier shown diagrammatically at20. In this case the pipe 16 is connected to the output of the amplifier20, the input of which is supplied with pressurized fluid from an input21. The output pressure of fluid from the amplifier to the bellows iscontrolled by the pressure of fluid in a branch pipe 22 which is indirect communication with the nozzle 19. The output pressure may also becontrolled by fluid pressure in a pipe 23, which is supplied from thesame source as are the inlet 21 and nozzle 19. The pipe 23 incorporatesa variable fluid resistor 24 to give fine control of the amplifieroutput pressure in the pipe 16.

The pressure in the pipes 22 and 23 may be substantially less than thatat the inlet 21.

FIG. 3 shows a form of tensioning device especially suitable for use inconnection with steel prestressing cables or other wires of substantialstiffness. In this case the wire, shown at 30, is passed around acapstan drum shown diagrammatically at 31, having a shaft 32 which isfreely rotatable in bearings 33 on a fixed structure 34. The shaft 32carries the disc 35 of a disc brake which is operated by the pressurizedfluid in the pipe 16.

In place of the spring 18 shown in FIGS. 1 and 2, the loop 17 issuspended from a resilient diaphragm 3'6 mounted peripherally on thefixed structure 34 adjacent the nozzle 19.

An increase in pressure in the pipe 16 tends to apply the brake, while adecrease tends to release it.

In other respects the arrangement shown in FIG. 3 is generally similarto that in FIG. 2, movement of the diaphragm 36 in response to changesin output tension of the wire 30 producing a feedback effect whichcauses the brake to be operated in a manner such as to tend to cancelthe change in output tension.

A pneumo-hydraulic or other valve may if necessary be incorporated inthe pipe 16 in FIG. 3.

A drum brake may be used instead of a disc brake.

The diaphragm 36 may be substituted for the spring 18 in devices such asthose shown in FIGS. 1 and 2; and in FIG. 3 the spring 18 may be used inplace of the diaphragm. However, any other suitable device may beemployed for varying the back pressure in the nozzle 19 in response tochanges in output tension of the thread.

FIGS. 4 and show one form of tensioner 40 which may be substituted forthe tensioner 11 in devices according to the invention for use withtextile threads and threads of similar size.

The tensioner 40 includes two dished washers 41 and 42 which are freelyrotatable about a fixed post 43. The lower washer 42 is constrainedagainst axial movement. The bellows 44, connected with the pipe 16,bears on the upper washer -41. The thread passes between the washers andmakes a partial turn around the post 43.

Variation in the fluid pressure within the bellows 44 4 varies the forceapplied to the thread by the washers 41 and 42, and thus varies thetension.

In the modified version of tensioner 60 shown in FIG. 6, a collapsiblebag 61 is substituted for the bellows 44. The mode of operation of thetensioners 44 and 60 is otherwise the same.

Many other variations are possible on the arrangements described above:some of these will now be briefly mentioned by way of example.

In the tensioner 11 (FIGS. 1 and 2), the bars 12 and 13 may be notchedto provide guides for the thread. They may be in the form of posts orpulleys, or any other device suitable for kinking the thread so as toapply a predetermined tension as described.

There may in some cases only need to be one bar 12.

The bellows in the tensioner 11 may be replaced by a bag such as the bag61 (FIG. 6). Any other suitable expandable fluid-tight device mayhowever be used in the tensioners 11, 40, 60.

The tensioner 11, 40 or 60, the spring 18 (or equivalent device) andnozzle 19 may all be incorporated together in a single unit, for examplea compact plastics moulding. If a fluid amplifier is included, this mayalso be incorporated in the same unit.

The fluid used may be a liquid or a gas. Especially in the absence ofmeans for preventing loss of gas to the atmosphere from the nozzle, orfor collecting for re-use a liquid ejected from the nozzle, a verysuitable fluid is compressed air. This may for example be supplied froma small auxiliary compressor driven by a main drive motor of the machinein which the tensioning device is incor porated.

The fiuidic amplifier may if desired be a multi-stage, instead of asingle-stage amplifier.

Devices according to the invention may be adapted to control the tensionof a number of threads simultaneously. For example the separate threadsin a group of threads may each pass through a separate tensioner, and beassociated with a separate spring 18 and nozzle 19, all the tensionersbeing controlled by fluid in a common feedback pipe, to which all thepipes 16 are connected, and which communicates with all the nozzles 19so as to be responsive to the mean tension of the threads in the group.

It will be understood that the mode of operation of the control systemmay be inverted, that is to say the spring 18 or diaphragm 36- (orequivalent device) may be so arranged as to increase the back pressureat the nozzle 19 in response to an increase in output tension in thethread; the tensioner, or the brake ('FIG. 3), or equivalent device isthen made to decrease the tension in response to increases in the backpressure. This may be done in the case of the tensioners 11, 40 and '60by modifying the design of the tensioner so that expansion of thebellows 14 or 44 or bag 61 decreases the tension. In the case of abrake, this may be modified by arranging for the brake to be applied bya decrease in fluid pressure.

Alternatively, where a fluidic amplifier is incorporated it may be ofthe negative type, i.e. one in which an increase in the control pressurein pipe 22 produces a decrease in the output pressure in pipe 16.

We claim:

1. A tensioning device for interposition between material supply andreceiving devices between which a flexible elongate material passes,comprising:

controllable retarding means engaging the material as it passes betweenthe supply and receiving devices to apply a variable retarding force tothe material, said means including an expansible resilient fluidreceiver having a fluid inlet duct for admitting thereto fluid underpressure and a movable output part engaging the retarding means to varythe retarding force applied by the retarding means to the material independence upon the fluid pressure in the receiver,

a tension sensing device having a sensing member engaged by the materialas it passes from the said retarding means towards the receiving deviceand a resilient biasing means biasing the sensing member to a biasposition, the sensing member being deflected by the material from thebias position as the tension in the material increases,

a fluid supply conduit having a flow restrictor, downstream thereof afluid escape nozzle disposed adjacent a part of the tension sensingdevice whereby movement of that part varies the rate of escape of fluidthrough the nozzle,

an outlet conduit located between the nozzle and the flow restrictor,

a fluid pressure amplifying device having: a control inlet ductconnected with the said outlet conduit; a supply inlet duct forreceiving fluid under constant pressure from a source of such fluid; anoutlet duct connecting with the fluid inlet duct of the fluid receiver;the control inlet duct, the supply inlet duct and the outlet ductcommunicating with one another in the amplifying device so that the flowof fluid in the control inlet duct interacts with the flo-w of fluidfrom the supply inlet duct so as to vary the flow of fluid from thesupply inlet duct to the outlet duct and hence to the fluid receiver.

2. A tensioning device according to claim 1, wherein the fluid pressureamplifying device has a second control inlet duct communicating with theother ducts in the amplifying device and being connected with anadjustable source of fluid under pressure for providing in theamplifying device a constant flow of fluid acting in opposition to thatprovided by the first-mentioned control inlet duct whereby to vary thepressure in the outlet duct in proportion to the difference in the fluidpressures in the two control inlet ducts.

3. A tensioning device according to claim 1, wherein the retarding meanscomprises a pair of washers having raised rims which face one anotherand which engage on opposite sides of the material passing to thereceiving device,

the retarding means and the expansible fluid receiver being mountedadjacent one another between opposed spaced surfaces of a fixed framemember, the frame member having projecting from one of its surfaces afixed pin on which the washers are freely carried for rotation, theexpansible fluid receiver being positioned to press the washers togetherwhereby to cause them to exert the retarding force on the materialpassing to the receiving device.

References Cited UNITED STATES PATENTS 2,098,422 11/1937 Keen et al242156.2 2,343,181 2/1944 Heinz 24275.43 2,610,813 9/1952 Campbell 2422,642,236 6/1953 Heizer 242 2,667,311 1/1954 Packer et a1 24275.432,714,494 8/1955 Wentz 242155 2,964,440 12/ 1960 Stevens 24275.43 X3,072,360 1/1963 Cruz 242154 FOREIGN PATENTS 1,241,232- 8/1960 France.

STANLEY N. GILREATH, Primary Examiner U.S. Cl. X.R. 242-154, 155

